1. Field of the Invention
The technology disclosed herein relates to radiation shielding systems generally, and more particularly, to a method, apparatus, and system for providing radiation shielding for non-invasive inspection systems.
2. Discussion of Related Art
Explosive detection systems and other types of inspection systems typically use radiation-based scanners, such as x-ray line scanners, x-ray CT scanners, and coherent x-ray scatter scanners, to examine bags (pieces of passenger baggage) for the presence of one or more alarm objects (explosives, weapons, illegal drugs, contraband, product components, and the like). In certain types of inspection systems, such as explosive detection systems, one or more shielding curtains typically blocks the entrance and exit of an x-ray scanner, since highly concentrated dose of high-energy radiation from the scanner can damage human tissue if the dose is too high. Some shielding curtains (hereinafter, “sheet curtains”) are formed of solid sections of material. More commonly, radiation-shielding curtains (hereinafter, “strip curtains”) are formed of multiple adjoining slats, each of which is aligned with adjacent slats to form a common plane.
FIG. 1, a sectional, perspective view of a conventional explosive detection system (EDS) 100, provides an example of how radiation-shielding curtains are typically arranged. In FIG. 1, a conveyor belt 101, positioned on a base 102, extends from one end of the EDS 100 to the opposite end of the EDS 100. The base 102 houses one or more conveyor belt motors (not shown), a computer (not shown), and one or more components of an x-ray scanner 103. A housing 104 rests on the base 102. A tunnel 105 formed in the housing 104 extends from one end of the housing 104 to the opposite end of the housing 104, and encloses the conveyor belt 101.
The x-ray scanner 103, positioned within a center portion of the housing 104, includes a scanning area 106, into which the conveyor belt 101 introduces one or more scannable objects. Configurations of the scanning area 106 will vary depending on the type of x-ray scanner used. For example, if an x-ray CT scanner is used, the scanning area 106 will be enclosed by a circular, movable gantry, to which an x-ray source and one or more detectors are fixedly attached.
Multiple, closely-spaced, strip curtains 107 hang suspended within the housing 104 over a portion of the conveyor belt 101. The portion of the conveyor belt over which the strip curtains 107 are positioned extends from an entrance 108 of the EDS 100 to an entrance 109 of the scanning area 106. In a like manner, parallel, planar rows of strip curtains 110 hang suspended within the housing 104 over another portion of the conveyor belt 101. This other portion of the conveyor belt 101 extends from the exit 111 of the scanning area 106 to the exit 112 of the housing 104.
In use, pieces of luggage (hereinafter, “bags”) may be loaded onto the conveyor belt 101 at the entrance 108 of the tunnel 105. Supported by the conveyor belt 101, the bags proceed through the EDS 100 in the direction of arrow 113 (from the EDS 100 entrance 108 to the EDS 100 exit 112). Enroute through the EDS 100, each bag passes through the scanning area 106 and is scanned by the x-ray scanner 103. After being scanned, the bags are transported by the conveyor belt 101 to the EDS 100 exit 112 and ejected from the EDS 100.
Aligning strip curtains in a common plane in the conventional manner, as shown in FIG. 1, has disadvantages. Chief among such disadvantages is that bags occasionally jam as they pass through the shielding curtains. When shielding curtains are arranged in parallel, planar rows, jamming occurs because most or all of the slats will contact a bag simultaneously, which traps the bag(s) in the strip curtain(s) even though the conveyor belt supporting the bag(s) continues to move. Another disadvantage associated with conventional strip curtains, such as those illustrated in FIG. 1, is that the slats from one strip curtain often entangle the slats of one or more other strip curtains.
One or more solutions are needed, which attenuate radiation produced by a radiation-based scanner while simultaneously permitting objects to enter and exit the scanner without jamming.